Ruby & GCsEntendendo Gerenciamento de Memória

"G1 GC is an incremental parallel compacting GC that provides more predictable pause times compared to CMS GC and Parallel Old GC. By

introducing a parallel, concurrent and multi-phased marking cycle, G1 GC can work with

much larger heaps while providing reasonable worst-case pause times."

Obsoletos Atuais

1.8.6 1.9.3

1.8.7 2.0.0

1.9.2 2.1.1

#include<stdio.h> int main() { int *ptr_one; ! ptr_one = (int *)malloc(sizeof(int)); ! if (ptr_one == 0) { printf("ERROR: Out of memory\n"); return 1; } ! *ptr_one = 25; printf("%d\n", *ptr_one); ! free(ptr_one); ! return 0; }

#include<stdio.h> int main() { int *ptr_one; ! ptr_one = (int *)malloc(sizeof(int)); ! if (ptr_one == 0) { printf("ERROR: Out of memory\n"); return 1; } ! *ptr_one = 25; printf("%d\n", *ptr_one); ! free(ptr_one); ! return 0; }

#include<stdio.h> int main() { int *ptr_one; ! ptr_one = (int *)malloc(sizeof(int)); ! if (ptr_one == 0) { printf("ERROR: Out of memory\n"); return 1; } ! *ptr_one = 25; printf("%d\n", *ptr_one); ! free(ptr_one); ! return 0; }

#include<stdio.h> int main() { int *ptr_one; ! ptr_one = (int *)malloc(sizeof(int)); ! if (ptr_one == 0) { printf("ERROR: Out of memory\n"); return 1; } ! *ptr_one = 25; printf("%d\n", *ptr_one); ! free(ptr_one); ! return 0; }

0000 0000

0000 0000

0000 0000

0001 1001

#include<stdio.h> int main() { int *ptr_one; ! ptr_one = (int *)malloc(sizeof(int)); ! if (ptr_one == 0) { printf("ERROR: Out of memory\n"); return 1; } ! *ptr_one = 25; printf("%d\n", *ptr_one); ! free(ptr_one); ! return 0; }

0000 0000

0000 0000

0000 0000

0001 1001

40 bytes livres

Slot (40 bytes)

Heap (ex 6 slots)

Slot (40 bytes)

Heap (ex 6 slots)

Instância de RVALUE

typedef struct RVALUE { union { struct { VALUE flags; /* always 0 for freed obj */ struct RVALUE *next; } free; struct RBasic basic; struct RObject object; struct RClass klass; struct RFloat flonum; struct RString string; struct RArray array; struct RRegexp regexp; struct RHash hash; struct RData data; struct RTypedData typeddata; struct RStruct rstruct; struct RBignum bignum; struct RFile file; struct RNode node; struct RMatch match; struct RRational rational; struct RComplex complex; struct { struct RBasic basic; VALUE v1; VALUE v2; VALUE v3; } values; } as; #if GC_DEBUG const char *file; VALUE line; #endif } RVALUE;

RVALUE

struct RString { struct RBasic basic; union { struct { long len; char *ptr; union { long capa; VALUE shared; } aux; } heap; char ary[RSTRING_EMBED_LEN_MAX + 1]; } as; };

RSTRING(str)->as.heap.ptr

Slot (40 kb)

Heap (ex 6 slots)

Instância de RVALUE

Dados do RVALUE

Slot (40 kb)

Heap (ex 6 slots)

Instância de RVALUE

Dados do RVALUE

Slot (40 kb)

Heap (ex 6 slots)

Instância de RVALUE

Dados do RVALUE

Mark and Sweep GC

Full Marking and Full Sweep GC

• Slots de mesmo tamanho (não há problema com fragmentação)

• Quanto mais heaps, mais lento

• Fase de marcação conservadora

• pode haver “leaks” (ex. constantes)

• Processo “Stop-the-World"

Master Unicorn ou Passenger

Rails App

NGINX

Rails App

Rails App

fork() fork()

request

150mb 150mb 150mb

Copy on Write (CoW)

só copia o trecho da memória quando for modificada

“Mark Bit Map”

Bitmap Marking GC

Full Bitmap Marking and Full Sweep GC

Master Unicorn ou Passenger

Rails App

NGINX

Rails App

Rails App

fork() fork()

request

150mb 100mb 100mb

Mark Sweep Mark Sweep Mark Sweep

Mark Mark Mark

Lazy Sweep GC

Full Bitmap Marking and Lazy Sweep GC

https://gist.github.com/akitaonrails/10212233

http://u.akita.ws/samsaffron_ruby20

RUBY_GC_MALLOC_LIMIT=30000000 \

RUBY_HEAP_MIN_SLOTS=800000 \

bundle exec rails server

RUBY_GC_MALLOC_LIMIT 8.000.000 30.000.000

RUBY_HEAP_MIN_SLOTS 10.000 800.000

env_gc_malloc_limit_in_mb 7.6mb 26.6mb

total_gc_runs 105 65

heaps_with_used_slots 1.089 1.477

total_heaps_allocated 1.958 1.965

total_heaps_allocated_in_mb 30.6mb 30.7mb

heaps_to_allocate_next_gc 869 0

2.49Mb

71.9Mb

GC Anterior

Weak Generational Hypothesis

“Most young objects die young"

Young Generation (Eden)

Old Generation (Tomb)

Generational GC

Copying Garbage Collector

From-Heap

To-Heap

From-Heap

To-Heap

Mark-Compact GC

Mark Copy Compact Heap Swap GC

• “Stop-and-Copy”

• Sweep precisa ir slot a slot, neste é só considerar tudo no primeiro heap como livre

• Gerenciamento interno de ponteiros

• Feito para corrigir fragmentação

• Ruby tem slots de mesmo tamanho

• Não suporta Copy-on-Write

Ruby 2.1.x

Shady vs Non-Shady

Ruby Object

Write Barrier (Non-Shady only)

Ruby Array

Shady Object

Non-Shady Object (Sunny)

Mark bitmap (mark_bits[])

Shady bitmap ( rememberset_bits[])

Objetos "Old" 96.4%

Objetos "Young" 3.6%

Objetos "Shady" 1.5%

Mark Mark Mark

Major GC

Minor GC

2.49Mb

71.9Mb

Restricted Generational GC (RGenGC)

Full M&S for Shady, Generational for Non-Shady

• Partial Markings, Lazy Sweeps = Menos Stop

• Shady objects não vão para o Tomb

• Write Barriers (referência old para new - non-Shady only)

• Compatível com extensões C (Shady)

• Objetos em Tomb só são remarcados em Full Mark

http://u.akita.ws/samsaffron_ruby21

ruby-trunk e ruby 2.1.2 (não lançado)

http://u.akita.ws/samsaffron_ruby21

< 1.3!(+ major GC)

RUBY_GC_MALLOC_LIMIT_MAX=8000000 \

RUBY_GC_OLDMALLOC_LIMIT_MAX=8000000 \

RUBY_GC_HEAP_OLDOBJECT_LIMIT_FACTOR=0.9

bundle exec rails server

força GC por diminuir o teto

basicamente desabilita minor GC

(de volta a Ruby 2.0.0)

RUBY_GC_MALLOC_LIMIT_MAX 3210241024 8000000

RUBY_GC_OLDMALLOC_LIMIT_MAX 12810241024 8000000

RUBY_GC_HEAP_OLDOBJECT_LIMIT_FACTOR 2.0 0.9

RUBY_GC_HEAP_INIT_SLOTS 10000 300000

RUBY_GC_HEAP_FREE_SLOTS 4096 300000

RUBY_GC_HEAP_GROWTH_FACTOR 1.8 1.25

RUBY_GC_HEAP_GROWTH_MAX_SLOTS (no limit) 150000

(obs: monitore, mensure, tuning, mensure de novo!)

http://tmm1.net/ruby21-rgengc/

• Objetos vão para Tomb se sobreviverem 1 GC

• Objetos podem ir para Tomb cedo demais

• Eden - Survivor - Tenured - Permanent

• RGENGC_THREEGEN mode (experimental)

• Parallel Marking (ex. em Thread separada)

• Tri-Color Marking (talvez)

• Futuro: Incremental Major Phase (major GC menores)

Java• Young Generation

• -XX:+UseSerialGC (copying collector)

• -XX:+UseParallelGC (copying collector multi-thread)

• -XX:+UseParNewGC

• Old Generation

• -XX:+UseParallelOldGC

• -XX:+UseConcMarkSweepGC

Master Unicorn ou Passenger

Rails App

NGINX

Rails App

Rails App

request

190ms 190ms 190ms

50ms de Full GC!

Master Unicorn ou Passenger

Rails App

NGINX

Rails App

Rails App

request

140ms 140ms Full GC

Executa Full GC quando não receber request

OOBGC

Out-of-Band Major GC

Pausas foram de 125ms para 50ms

http://tmm1.net/ruby21-oobgc/

http://u.akita.ws/rubymicroscope

Obrigado!@akitaonrails

slideshare.net/akitaonrails www.akitaonrails.com